The primary steps responsible for muscle insulin resistance to the pathogenesis of non-insulin dependent diabetes mellitus are unknown. This study is part of a program project the purpose of which is to distinguish between acquired and hereditary mechanisms for insulin resistance by characterizing the molecular mechanisms responsible for insulin resistance in nondiabetic subjects who have a strong genetic background for NIDDM and a high rate of progression to NIDDM. In this study, insulin resistance and NIDDM alterations in insulin-stimulated phosphorylation will be examined.